Permanent magnet electrodynamic loud-speaker structure adapted for ready assembly



Dec. 5, 1950 s. E. LEVY 2,532,414

PERMANENT MAGNET ELECTRODYNAMIC LOUDSPEAKER STRUCTURE ADAPTED FOR READY ASSEMBLY Filed Dec. 31, 1946 INVENTOR SIDNEY E. LEVY ATTORNEYS Patented Dec. 1954) rnaMaNE r MAGNET psornonrnamrc oUn-sP sKER sTiaUc'rUnE AioAr'rED FOR READY ASSEMBLY Sidney E. Levy, Brooklyn, N. Y., assignor to University Loudspeakers, 1110., New York, N. Y., a

corporation of New York Application December 31, 1946, Serial No. 719,433

4 Claims. 1

The present invention relates to a loudspeaker construction, and particularly to a construction of a permanent magnet speaker in which the permanent magnet is of the bar type and is possessed. of one polarity at the center and the opposite polarity at its outer ends. A generally similar structure was shown in my application Serial Number 684,064, filed July 16, 1946, now abandoned, but that structure required a rather different assemblage. In the present invention the structure is so designed as to render the assemblage of the diaphragm supporting rim, together with inner and outer pole pieces and the magnet proper, as well as the casing, extremely simple. Thus, it is possible to assemble the loudspeaker of the instant invention rapidly and with the utilization of unskilled labor. Additionally, it is possible for a magnet or a cone assembly to be replaced in the field without difiiculty.

It is an object of my invention to provide a loudspeaker construction utilizing a doublypolarized bar or plate magnet in which the assembly of the elements is extremely simply and economically performed.

It is another object of my invention to provide such a structure in which the elements making up the assembly are themselves readily manufactured at low cost.

It is another object of my invention to provide a loudspeaker which is so simply assembled as to render it possible for a repairman in the field to replace a broken or otherwise inoperative magnet or cone without special tools of any kind.

It is another object of the invention to provide means whereby the voice coil of the diaphragm becomes automatically centered in the air gap of the magnet keepers.

Other objects and features of the invention will be apparent when the following description is considered in connection with the annexed drawings, in which:

Fig. 1 is a top plan view of the loudspeaker of my invention with the diaphragm broken away and with part of the frame or basket broken away in order to more clearly show the construction of the magnet and magnet pole pieces; and

Fig. 2 is a cross-sectional view of the loudspeaker of Fig. 1, the section being taken along the plane of the line 22 of Fig. 1.

Referring now to the drawings, the loudspeaker of the present invention comprises a framework or basket it having the usual annular form and having the usual cutouts H in order to lessen its weight and to permit release of the back wave. This basket H5 is provided with a rim to which the diaphragm shown in Fig. 1 and indicated by dotted lines at 58 of Fig. 2, is suitably fastened, as by cementing. In the present instance, the basket it is additionally provided near the base thereof with an inturned rim Hi, having lugs i5 bent off therefrom and extending outwardly, as seen particularly in Fig. 2. The inturned portion Hi is provided with a central aperture i5 and is likewise provided with projections i! which are arranged in any suitable manner, and in the particular instance in a rectangular formation. These projections i? may be small pins fastened to the rim M or may be formed integrally with rim portion 5 near the central aperture thereof by means of a stamping operation.

The usual outer pole piece or keeper i8 is generally rectangular in shape, as seen in plan, and has a central portion elevated above the periphery thereof so that the inner pole piece 20 may be arranged within an aperture 2i of the outer pole piece 28 to form the usual magne c gap into which projects a portion of the diaphragm l3 carrying the voice coil. As is usual, the diapl ragm 13 carries an outwardly-projecting annular flexible rim 23 commonly known as a spider at its apex. ch annular spider is cemented to the rim portion is adjacent edge 24, as seen in Fig. 2. The or outer pole piece i8 is provided with de ssions 25 arranged in the same formation as are the projections ll of the rim M. Thus, th pole piece it ay be assembled against the rim l t and located in definite position.

A l'lf" --li8,'gl'3tli3. ge erally conio 'twshaped washer is provided, this washer be g provided with holes, depresuons or cutaway areas thereh 1112, be arranged in j suitable form,

the present instance are the same rectan ular are the projections ii and the depressions 25. The washer 25 can thus be definitely located with respect to the outer pole piece since this pole piece carries projections 2i likewise arranged in a rectangular formation.

If desired, the non-magnetic centering washer 26, need not have the aforementioned holes or depressions. It may be accurately located mere- 1y by having the outside diameter of the washer form a close fit with the inside diameter formed by the projecting pins on the keeper, or outer pole piece I 8.

, of the invention.

Although not necessary to the construction, it is preferable that the depressions 25 and projections 271' be formed simultaneously merely by stamping the member 58, thus extruding the metal in the form of pins and leaving the depressions 25. The inner periphery of the washer 25 is of substantially the same diameter as the diameter of the pole piece 2i? and, consequently, by definitely locating the washer with respect to the outer pole piece, the inner pole piece may also be properly located with respect to the outer pole piece and the magnetic gap thus made uniform.

Thus, in assembling the speaker, it is only necessary to place the outer pole piece IS in position on the rim i l, with the projections ll of the rim extending into depressions 25 of the keeper; then place the washer 26 upon the outer pole piece, with the depressions or holes 28 mating with the projections 2? of the keeper l8. Following this, the doubly-polarized bar magnet with the inner pole piece 26 in approximate position thereon, may be placed with its edges coinciding with the edges of the outer pole piece and thus the magnetic circuit will be completed through the outer pole piece, the magnetic gap, and the inner pole piece.

The magnet 36 is held in its assembled posiby placing a cup-shaped cover piece 5i, having an outwardly-extending annular rim 32, in position so that the rim 32 fits against the inwardly-extending rim it of the basket it. The rim 32 is provided with slots at a plurality of points on its circumference through which the lugs or ears l5 oil the basket I 6 project, these lugs being subsequently bent over against the rim 32 to hold the cup 31 in position. Obviously, the cup iii in turn holds the magnet against the keeper so that the entire structure is rigidly held in its assembled relationship. If it becomes necessary to replace the magnet, it will be seen that it is only necessary to bend the lugs [5 to a vertical position, as seen in Fig. 2, remove the cup 35, then remove the magnet and substitute a new one therefor, subsequently reversing the procedure and reinstalling the cover or cup 3E. 'The magnet 38 utilized in the structure above described has curved sides 33 and a varying thickness producing a curved base 3%, as shown in the drawings. This is done in order to produce uniform flux density throughout the magnet 33 and is in conformance with the structure shown and claimed in my copending application Serial No. 719,432 filed Dec. 31, 1946. However, it is entirely possible to utilize the same assembly methods and the same general structure when a doubly-polarized magnet of rectangular shape and having a plane base, such as that illustrated in my, copending application, Serial Number 684,864, filed July 16, 1946, is utilized. Similarly, in the event it is desired to replace a damaged diaphragm or voice coil, the entire basket E8 together with the cone and spider cemented thereto may be removed, and be readily replaced. The centering of the new cone assembly is assured since it is only necessary to fit the projecting pins of the inner ring it of the basket into the corresponding holes on the outer pole piece.

While I have described a preferred form of my invention, it will be understood that other forms may be devised without departing from the spirit Consequently, I wish to be limited not by the foregoing description, which was given solely for the purpose of illustration, but only by the appended claims.

What is claimed is:

1. In a transducer of the type described, having a frusto-conical diaphragm supporting basket and a permanent magnet structure supported thereon to produce an annular magnetic gap into which a voice coil carried by the diaphragm projects, means for locating the elements of the magnetic structure relative to the diaphragm and voice coil, comprising, in combination, an inwardly-extending flange at the apex of the basket, projections on said flange, an outer magnetic pole piece having a central aperture therein, hollow bosses on said pole piece into which said projections fit to fix the position of said pole piece relative to said diaphragm, an inner pole piece, a non-magnetic washer mounted on said inner pole piece and having an outwardly-extending fiange in contact with said outer pole piece, depressions in said washer flange into which said bosses fit to locate said washer in a definite position with respect to said outer pole piece to thereby fix the position of said inner pole piece with respect to said outer pole piece and form an annular magnetic gap in which the voice coil is centered, a doubly-polarized plate magnet in contact with said inner and outer pole pieces, respectively at the center and the ends thereof, and a cup-shaped member for holding said pole pieces and magnet in adjusted position, said member bearing against the base of said magnet and being fixed at its rim to the said flange of the basket.

2. In a transducer of the type described, having a .frusto-conical diaphragm supporting basket and a permanent magnet structure supported thereon to produce an annular magnetic gap into which a voice coil carried by the diaphragm projects, means for locating the elements of the magnetic structure relative to the diaphragm and voice coil, comprising, in combination, an inwardly-extending fiange at the apex of the basket, a plurality of projections on said flange, an outer e magnetic pole piece having a central aperture therein, hollow bosses on said pole piece into which said projections fit to fix the position of said pole piece relative to said diaphragm, an inner pole piece, a non-magnetic washer mounted on said inner pole piece and having an outwardly-extending flange in contact with said outer pole piece, depressions in said flange into which said bosses fit tolocate said washer flange in a definite position with respect to said outer pole piece to thereby fix the position of said inner pole piece with respect to said outer pole piece and form an annular magnetic gap in which the voice coil is centered, a doubly-polarized plate magnet in contact with said inner and outer pole pieces, respectively at the center and the ends thereof, and a cup-shaped member for holding said pole pieces and magnet in adjusted position, said member bearing against said magnet and being fixed at its rim to the said flange of the basket.

3. In a transducer of the type described, having a frusto-conical diaphragm supporting basket and a permanent magnet structure supported thereon to produce an annular magnetic gap into which a voice coil carried by the diaphragm proj ects, means for locating the elements of the magnetic structure relative to the diaphragm and voice coil, comprising, in combination, an inwardly-extending fiange at the apex of the basket, projections on said flange, an outer magnetic pole piece having a central aperture therein,

hollow bosses on said pole piece into which said projections fit to fix the position of said pole piece relative to said diaphragm, an inner pole piece, a non-magnetic washer mounted on said inner pole piece and having an outwardly-extending flange in contact with said outer pole piece, depressions in said washer flange into which said bosses fit to locate said washer in a definite position with respect to said outer pole piece to thereby fix the position of said inner pole piece with respect to said outer pole piece and form an annular magnetic gap in which the voice coil is centered, a doubly-polarized plate magnet in contact with said inner and outer pole pieces, respectively at the center and the ends thereof, a cup for holding the said magnet and pole pieces in their predetermined positions, said cup having a flange engaging the flange of said basket, said basket flange having lugs struck therefrom, and said cup flange having slots therein, said lugs being bent over after passing through said slots to thereby hold said magnet and pole pieces in their adjusted position relative to the basket and voice coil.

4. In a transducer of the type described, having a frusto-conical diaphragm supporting basket and a permanent magnet structure supported thereon to produce an annular magnetic gap into which a voice coil carried by the diaphragm projects, means for locating the elements of the magnetic structure relative to the diaphragm and voice coil, comprising, in combination, an inwardly-extending flange at the apex of the basket, a plurality of projections on said flange, an outer magnetic pole piece having a central aperture therein, hollow bosses in said pole piece into which said projections fit to fix the position of said pole piece relative to said diaphragm, an inner pole piece, a non-magnetic washer mounted on said inner pole piece and having an outwardlyextending flange in contact with said outer pole piece, depressions in said flanges fitting over said bosses to locate said washer flange in a deflnite position with respect to said outer pole piece to thereby fix the position of said inner pole piece with respect to said outer pole piece and form an annular magnetic gap in which the voice coil is centered, a doubly-polarized plate magnet in contact with said inner and outer pole pieces, respectively at the center and the ends thereof, a cup for holding the said magnet and pole pieces in their predetermined positions, said cup having a flange engaging the flange of said basket, said basket flange having lugs struck therefrom, and said cup flange having slots therein, said lugs being bent over after passing through said slots to thereby hold said magnet and pole pieces in their adjusted position relative to the basket and voice coil.

SIDNEY E. LEVY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS- Number Name Date 1,766,473 Wente Jan. 24, 1930 1,838,027 Clarke Dec. 22, 1931 2,046,515 Jensen July 7, 1936 FOREIGN PATENTS Number Country Date 491,509 Great Britain Sept. 5, 1938 874,258 France Aug. 3. 1942 

